Dual-functionality of Bismuth oxide (Bi₂O₃): Catalyst and dielectric barrier for efficient PFOS degradation in plasma...

Perfluorooctane sulfonate (PFOS), a typical per- and polyfluoroalkyl substance (PFASs) known for its extreme persistence and bioaccumulative toxicity, continues to pose ecological risks despite global production restrictions. Existing removal methods face challenges like low degradation and defluorination rates. This study employed a dielectric barrier discharge plasma (DBD-plasma) method with oxygen-vacancy-rich Bi₂O₃ as a bifunctional catalyst, achieving efficient removal of PFOS while functioning as a dielectric barrier. Plasma treatment transformed Bi₂O₃ into layered structures and generated high-valence Bi(V/VI) species. The system achieved a removal efficiency of 96.6 % and defluorination efficiency of 68.6 % for 10 mg/L PFOS in 30 min at an input power of 50 W. Quenching experiments and optical emission spectrometry (OES) results confirmed hydrated electron (e_aq^-) as the key species in driving PFOS degradation. Eight carboxylated and hydroxylated products were identified, differing from the conventional short-chain PFCAs. Cyclic experiments demonstrated the superior stability of the system, showing a 29.6 % increase in degradation rate compared to direct catalyst addition at the same dosage. These findings advance understanding of PFOS degradation via plasma technology, offering a promising approach for PFAS remediation.